Piston ring assembly



A. P. FALL Filed Aug. 3. 1940 gf@ W m V www? 25M May so, 1944.

PISTON RING ASSEMBLY Patented May 30, 1944 `UNITEDQSTATES PATENT OFFICE Application August 3, 1940, Serial No. 350,229

3 Claims.

rIhis invention relates to piston rings, that is, metallic expansive rings located in grooves in a piston for preventing the leakage of gas past the piston, and particularly to piston rings for internal combustion engines in which the piston rings not only serve to prevent leakage of gas past the pistons but also serves to control the amount of oil on the cylinder walls.

One of the principal objects of the present invention is to provide a pistonrng having narrow cylinder Wall engaging surfaces which will quickly Wear into a perfect fit with the cylinder wall, even if the cylinder wall is worn and slightly irregular.

Another object of the present invention is to provide a piston ring which will tend to support the upper end of the piston coaxially with the cylinder and thus lessen piston slap and oil pumping in an engine in which the pistons and cylinders are somewhat worn.

Another object of this invention is to provide a composite piston ring engaging the cylinder Wall alo-ng two or more lines extending around the cylinder and having spring means acting between the cylinder engaging portion of the ring and the piston.`

Other objects and features will appear from the following description and the appended claims taken in connection with the accompanying drawing, in which:

Figure 1 is a horizontal section through a piston showing one of the preferred forms of the invention in place;

Figure 2 is a side elevation of the embodiment of the invention shown vin Figure 1 mounted on a piston in a cylinder, the cylinder being shown in section, Y

Figure 3 is a cross section on the line III-III of Figure 1 looking in the direction of the arrows and on an enlarged scale;

Figure 4 is a cross section similar to Figure 3 showing a second form of the invention;

Figure 5 is a cross section similar to Figure 3 showing a third form of the invention;

Figure 6 is a cross section similar to Figure 3 showing a fourth form of the invention;

Figure 7 is a cross section similar to Figure 3 showing a fth form of the invention; and

Figure 8 is a cross section similar to Figure 3 showing a sixth form of the invention.

The form of the invention shown in Figures 1 to 3 comprises a pair of split rings or segments I0 and II formed of some suitable material, such as a high quality cast iron, and having the cross sections shown in Figure 3. As may be seen from Figure 3, the cross sections of the two segments I 0 and II are similar, one segment II being like the other segment Il) but inverted. The segment I0 comprises a main portion adapted to lie against one side of the groove I2 in the piston I3, and is formed with an integral ange Illa extending radially inwardly against the side of the groove I2. The outer face of the ring or segment I0 is formed with a set-back or marginal groove Ib, so that the width of the face of the ring that bears against the wall of the cylinder I4 is considerably narrower than the main portion of the ring Ill. The ring II is sim..

ilarly formed with an axially inwardly project-v ing flange I Ia lying against the bottom side of the ring groove I2 and with an offset or groove IIb.

The two rings or segments I0 and Il are heldA against the sides of the groove I2 and are pressed resiliently outward against the cylinder wall I-'I by means of a spring steel expanderring I5. The expander ring 'I5 lies between the flanges II'Ia and I Ia on the ring segments II! and I I, as shown in `Figure 3, and thus holds the segments I0 and II against the upper and lower sides of the pis ton ring groove I2. The expander ring I5, is not circular in plan but is approximately polygonal, as shown in Figure 1, the sides I5a of the polygon being concave and bearing against the bottom of the groove I2 and the corners I5b of the polygon being rounded andbearing against the back of the main portions of the ring segments I0 and II. The ring I5 is split at |50 in order that it may expand or contract as required by the ring segments II) and II and the cylinder i4 in which the piston ring assembly is being used. It may be noted from Figure 1 that the concave or relatively straight portions I5a of the expander ring I5` bear against the bottom of the groove I2 and that the corners I5b bear against the ring segments I0 and II, thus pressing the ring segments I0 and II radially outwardly with respect to the piston I3. With this arrangement, the exact pressure that may be desired between the ring segments I0 and II and the cylinder wall I4 may be secured, and this pressure will be uniformly distributed around,V

the entire circuoiference of the ring segments.

It will be noted that the construction shown in Figure 3 provides a slot between the ring segments I0 and II. At the points where the corners I5b of the expander ring press against the ring segments IIJ and II, this slot is closed, but it may readily be seen from Figure 1 that the concave portions Ia of the expander ring lie in is intended to function purely as a compression ring and lcomprises twoiring segments i and II, which may be identical with the ring segments in the form of the invention shown in Figures 1, 2 and 3, and a spring steel expander ring I8. The expander ring I8 is similar to the expander ring I in the form of the invention shown in Figures 1, 2 and 8 but is considerably nar-" rower. The width of the expander ring ld is such that it fits between the flanges Isa and IIa. of the ring segments I0 and Ii when the main portions of the ring segments lil and I l are in contact, as shown in. Figure 4, andthe piston ring groove I9 in the piston 22 is of such ay width as to accommodate the-ring segments It] and II inthis relation. t will be noted that, in the construction shown vin Figure there is no slot between the ring segments It and il and that the ring assembly therefore will not remove oil.

from the cylinder wall to any appreciable extent. If it is desired to remove oil at this point, however, a slot may beprovided.

The form of the invention shown in Figure 5 comprises a pair of ring segments ill andil, which may be identical with the` ring segments l0 and l i in the form of the invention shown in Figures 1, 2 and 3, a oating ring segment 22, and a spring steel expander ring 23. lThe expander ring 23 is similar to the expander ring Ifiin the rst form of the invention but is wider so that the slot between the two ring segments Ill and II is relatively wide, thus providing room between the ring segments Ill and Ii for the floating ring segment 22. The groove 24 in the piston 25 is, of course,.wider than the groove l2 employed for the first form of the invention in order to accommodate the wider ring assembly.

The floating ring segment ,22 may be of cast iron o r steel and is of simple rectangular cross section. The ring segment 22 is split in the. same manner as the ring segments IQ and -i i and is pressed against the cylinder wall by the' spring expander ring 2,3 in the same way as the upper and lower ring segments Ii! and II. When the engine in which the ring assembly is used is in operation, the floating ring segment 22 moves up and down in the slot between the upper and lower ringl segments I ll and II and prevents the accumulation of any carbon orzother undesirable material. between the upper and lower ring segments, so that they will always be free to expand and contract as required `by the cylinder bore. Keeping the slot between the rings I i) and II clear is also of importance because of the oilvcontrcl function of they ring assembly shown in Figure 5. Obviously, if this slot were to become clogged by carbon, the oil control properties of the ring'assembly would be greatly irnpaired`- The form of the invention shown in Figure 6 comprises upper and lower ring segments 2i and 23 and a spring steel expander ring 29 located within a piston ring groover Sti in a piston 3|. The upper vring segment 2l may be identical with either of the ring segments I5 and Il in the form of the invention shown in Figures 1, 2 and 3 or it may have slightly different proportions, as shown. In any case, the ring segment 2'! is provided with a radially inwardly projecting lip 21a integral with the main portion of the ring segment and lying against one side of the ring groove 30.

The lower ring segment 28 may be formed of cast iron but is preferably formed of alloy steel and has a plain rectangular cross section, as shown, the width of the ring segment 28 being such that, with the upper ring segment 21, it fills the width of the ring groove 30. The spring steel expander ring 29 is generally similar to the "it to fit between the flange 27a on the upper liti ring segment 27 and the lower side of the ring groove 30.

The form of the invention shown in Figure 'l comprises two ring segments ,IIJ and II, which are identical with the ring segments lil and II in the form of the invention shown in Figures 1, 2` and 3, and two spring steel expander rings 33 and 34, all fitting within a single ring groove 35 in a piston 35, This construction differs from the one shownV in Figures 1, 2 and 3 chiefly in that both of the ring segments Il) and .EI have the same side up and in the use of two expander rings 33 and 3ft instead of a single expander ring. The ilange ma on the upper ring segment I0 lies flat against the upper side of the ring groove 35 but the flange IIa of the lower ring segment Il lies between the two expander rings 33 and 3A instead of lying against the bottom of the ringv groove.

The twofexpander rings 33 and 34 and the ring groove 35 are of such widths that the ring segments IIJ and Il are spaced from each other and from the bottom of the ring groove 35, thus providing two oil control slots 3'! and 38. This formlofthe invention therefore is very eiective in preventing excessive oil consumption.

` The form of the invention shown in Figure 8 i comprises a pair of ring segments 4U and il which are identical with each other and are of such a width that together they fill the Width of the ring groove in the piston 42. The faces of both of the ring segments and 3l are set back near their lower edges, as shown at lilla, and lila, so that the width Vof the face which bears against the, cylinder wall is substantially narrower than the over-all width of the ring segments. The two ring segments and 4I are pressed outwardly against the cylinder wall by means of a spring steel expander ring 42, which is similar in plan to the expander ring I5 shown in Figure 1 but whose width is equal to the width of 'the ring groove.

The various forms of ring assemblies shown in the drawings and described above may be used in various `combinations with each other and with conventional piston rings. For example, in ak piston having three ring grooves, the upper ring may be a plain compression ring of rectangular cross section, the second ring may be a compression ring of the type shown in Figure 6, and the third ring may be an oil ring of the type shown in Figures 1, 2 and 3. In a piston i having four ring grooves, the same arrangement of rings may be used in the first three grooves and a conventional one-piece oil ring used in the fourth groove. Another arrangement which is satisfactory .for three ring pistons is to provide a dual compression ring of the type shown in ligure 8 in the rst ring groove, a compression ring of the type shown in Figure 4 in the second ring groove, and an oil control ring of either the type shown in Figures 1, 2, and 3 or in Figure 5 in the third ring groove. These are only a few of the possible combinations which may be advantageously employed, and it will be obvious that numerous other possible combinations may be made and will perform effectively.

While I have shown and described only a few of the principal forms oi my invention, it is to be clearly understood that these are shown only by way of example and that my invention is not limited thereto but includes everything coming clearly within the terms of the following claims.

I claim as my invention:

1. A piston ring assembly comprising ring segments, said ring segments including upper and lower members having radially inwardly extending iianges and axially extending shoulder flanges, each of said shoulder flanges having an outer recessed edge providing a cylinder engaging surface of less width than the axial width of the member, a radially expansive spring expander seated between said radially extending flanges and against said axially extending shoulder flanges, and a floating ring segment between said upper and lower members seated against said spring expander and extending radially outward thereof to terminate ush with the cylinder engaging surfaces on said ring segments, said ring assembly being adapted to slidingly fit within a piston ring groove with the spring expander pressing against the bottom of the groove and against the ring segment members and the floating ring to hold them against the wall of a cylinder.

2. A piston ring assembly comprising a pair of spaced opposed ring segments, each of said segments having an axially extending main portion and a radially inwardly extending flange, the intersecting surfaces of said main portion and said flange on each of said segments extending in right angular relation, a spring expander ring between said flanges having unbroken parallel surfaces for maintaining said segments in spaced relation against the sides of a piston groove, said expander ring being seated against saidright angular intersecting surfaces, and a iioatng ring embracing said expander ring between said segments and being coextensive radially outward with said segments, said segments, floating ring and expander being adapted to t within a ring groove` of a piston with said expander pressing against the bottom of the groove for urging said segments and floating ring against the wall of a cylinder containing said piston.

3. A piston ring structure including spaced opposed ring segments each having an expander abutment shoulder spaced radially inward from its outer periphery and spaced axially inward from its outer end surface, an expander thrusting against said shoulders and holding the segments in axial alignment and in axial spacedl relation, and a oating ring enveloping the expander between the ring segments and extending radially outward from the expander to terminate flush with the outer peripheries of the segments.

ALBERT P. FALL. 

